Auto white balance correction value calculation device, method, program, and image pickup device

Abstract

A normal AWB (auto white balance) correction value is calculated based on inputted image data. Further, a face area is identified from the inputted image data and a face AWB correction value is calculated based on image data in the face area. Then, first feature data and second feature data are extracted from the inputted image data and image data in the face area, respectively. A total AWB correction value is calculated in accordance with at least one of the face AWB correction value and the normal AWB correction value based on a comparison result of the first feature data and the second feature data. Thus, an erroneous correction can be prevented in an AWB correction using a face detection function.

What is claimed is: 
     
       1. An auto white balance correction value calculation method comprising:
 obtaining image data; 
 calculating a normal AWB correction value, which is a first auto white balance (AWB) correction value, based on the obtained image data; 
 identifying a face area from the image data; 
 calculating a face AWB correction value, which is a second AWB correction value, based on the face area of the image data; 
 dividing the image data into a plurality of areas and extracting feature data from the areas; 
 extracting feature data from the face area; and 
 calculating a total AWB correction value in accordance with at least one of the face AWB correction value and the normal AWB correction value based on a comparison result of the feature data extracted from each divided area and the feature data extracted from the face area. 
 
     
     
       2. The auto white balance correction value calculation method according to  claim 1 , wherein
 a light source color is extracted from the face area as the feature data, and 
 a representative color of each divided area is extracted from each divided area as the feature data. 
 
     
     
       3. The auto white balance correction value calculation method according to  claim 2 , further comprising
 plotting the light source color extracted from the face area and the representative color extracted from each of the divided areas in a color space; wherein 
 in the comparison of the feature data extracted from each divided area and the feature data extracted from the face area, a number of representative colors extracted from the divided areas existing in a neighborhood of light source color extracted from the face area in the color space is considered. 
 
     
     
       4. The auto white balance correction value calculation method according to  claim 2 , further comprising:
 calculating differences between representative colors of specific areas among the representative colors of the areas and the light source color of the face area; and 
 calculating the total AWB correction value based on the differences. 
 
     
     
       5. The auto white balance correction value calculation method according to  claim 2 , further comprising:
 calculating differences between representative colors of specific areas among the representative colors of the areas and the light source color of the face area; and 
 calculating the total AWB correction value based on a value obtained by finding a weighted average of differences of a predetermined number of areas near the face area among the differences with a predetermined weight β, which is 0% or more and 100% or less, corresponding to the differences. 
 
     
     
       6. The auto white balance correction value calculation method according to  claim 1 , further comprising
 selecting one of the face AWB correction value and the normal AWB correction value as the total AWB correction value based on a comparison result of the feature data extracted from the areas and the feature data extracted from the face area. 
 
     
     
       7. The auto white balance correction value calculation method according to  claim 1 , further comprising
 calculating the total AWB correction value by obtaining a weighted average of the face AWB correction value and the normal AWB correction value with a predetermined weight α, which is 0% or more and 100% or less, based on the comparison result of the feature data extracted from the areas and the feature data extracted from the face area. 
 
     
     
       8. The auto white balance correction value calculation method according to  claim 2 , further comprising:
 obtaining a total light source color by finding a weighted average of the light source color of the image data and the light source color of the face area with a predetermined weight α which is 0% or more and 100% or less; and 
 calculating the total AWB correction value in accordance with the total light source color. 
 
     
     
       9. The auto white balance correction value calculation method according to  claim 1 , further comprising
 displaying the total AWB correction value. 
 
     
     
       10. The auto white balance correction value calculation method according to  claim 1 , further comprising
 displaying an area in which the feature data compared with the feature data of the face area is extracted. 
 
     
     
       11. The auto white balance correction value calculation method according to  claim 1 , further comprising:
 accepting selection of a face priority; and 
 changing the weight of the total AWB correction value in accordance with the face priority. 
 
     
     
       12. A non-transitory recording medium in which an auto white balance correction value calculation program causing a computer to execute the auto white balance correction value calculation is stored, the program comprising computer-executable instructions of:
 obtaining image data; 
 calculating a normal AWB correction value, which is a first auto white balance (AWB) correction value, based on the obtained image data; 
 identifying a face area from the image data; 
 calculating a face AWB correction value, which is a second AWB correction value, based on the face area of the image data; 
 dividing the image data into a plurality of areas and extracting feature data from the areas; 
 extracting feature data from the face area; and 
 calculating a total AWB correction value in accordance with at least one of the face AWB correction value and the normal AWB correction value based on a comparison result of the feature data extracted from each divided area and the feature data extracted from the face area. 
 
     
     
       13. An auto white balance correction value calculation device comprising:
 an image data input unit which inputs image data; 
 a normal AWB correction value calculation unit which calculates a normal AWB correction value, which is a first auto white balance (AWB) correction value, based on the image data inputted in the image data input unit; 
 a face area identification unit which identifies a face area from the image data; 
 a face AWB correction value calculation unit which calculates a face AWB correction value, which is a second AWB correction value, based on the face area of the image data; 
 an area feature data extraction unit which divides the image data into a plurality of areas and extracts feature data from the areas; 
 a face area feature data extraction unit which extracts feature data from the face area; and 
 a total AWB correction value calculation unit which calculates a total AWB correction value in accordance with at least one of the face AWB correction value and the normal AWB correction value based on a comparison result of the feature data extracted from each area and the feature data extracted from the face area. 
 
     
     
       14. The auto white balance correction value calculation device according to  claim 13 , wherein
 a light source color is extracted from the face area as the feature data, and 
 representative colors of the areas are extracted from the areas as the feature data. 
 
     
     
       15. The auto white balance correction value calculation device according to  claim 14 , further comprising
 a difference calculation unit which calculates differences between representative colors of specific areas among the representative colors of the divided areas and the light source color of the face area, wherein 
 the total AWB correction value calculation unit calculates the total AWB correction value based on the differences. 
 
     
     
       16. The auto white balance correction value calculation device according to  claim 14 , further comprising
 a difference calculation unit which calculates differences between representative colors of specific areas among the representative colors of the divided areas and the light source color of the face area, wherein 
 the total AWB correction value calculation unit calculates the total AWB correction value based on a value obtained by finding a weighted average of differences of a predetermined number of divided areas near the face area among the differences with a predetermined weight β, which is 0% or more and 100% or less, corresponding to the differences. 
 
     
     
       17. The auto white balance correction value calculation device according to  claim 13 , wherein
 the total AWB correction value calculation unit selects one of the face AWB correction value and the normal AWB correction value as the total AWB correction value based on a comparison result of the feature data extracted from the divided areas and the feature data extracted from the face area. 
 
     
     
       18. The auto white balance correction value calculation device according to  claim 13 , wherein
 the total AWB correction value calculation unit calculates the total AWB correction value by obtaining a weighted average of the face AWB correction value and the normal AWB correction value with a predetermined weight α, which is 0% or more and 100% or less, based on the comparison result of the feature data extracted from the divided areas and the feature data extracted from the face area. 
 
     
     
       19. The auto white balance correction value calculation device according to  claim 14 , further comprising
 a total light source color calculation unit which obtains a total light source color by finding a weighted average of the light source color of the image data and the light source color of the face area with a predetermined weight α which is 0% or more and 100% or less, wherein 
 the total AWB correction value calculation unit calculates the total AWB correction value in accordance with the total light source color. 
 
     
     
       20. The auto white balance correction value calculation device according to  claim 13 , further comprising
 a display unit which displays the total AWB correction value. 
 
     
     
       21. The auto white balance correction value calculation device according to  claim 13 , further comprising
 a display unit which displays an area from which feature data compared with the feature data of the face area is extracted. 
 
     
     
       22. The auto white balance correction value calculation device according to  claim 13 , further comprising
 a face priority selection unit which accepts selection of a face priority, wherein 
 the total AWB correction value calculation unit changes the weight of the total AWB correction value in accordance with the face priority. 
 
     
     
       23. An image pickup device comprising:
 an auto white balance correction value calculation device according to  claim 13 ; 
 an image pickup element which receives an object image through a photographing optical system and outputs an analog image signal indicative of the object image; 
 an image data output unit which converts the analog image signal to digital image data and outputs the digital image data to the image data input unit; and 
 a correction unit which corrects a white balance of the image data based on the total AWB correction value calculated by the auto white balance correction value calculation device.